Re: control/shutdown node removed on suspend?

["Durrant, Paul" <xadimgnik@xxxxxxxxx>]

On 04/05/2022 16:33, Marek Marczykowski-Górecki wrote:
> Hi,
>
> I've just got an interesting bug report - it seems Windows PV drivers (or
> something else?) remove control/shutdown xenstore node on suspend,
> instead of just writing empty string there (to ack the request).
> This makes subsequent suspend to fail, because toolstack does not adjust
> permissions of that node when writing to it (assuming it was set
> correctly during domain construction), which means domU has no longer
> write access to it and cannot acknowledge the request.
>
> TBH, I'm not sure where exactly this happens, could be also outside of
> PV drivers. But the issue doesn't apply for Linux VMs - that's why I
> think it is related to Windows PV drivers.
> https://xenbits.xen.org/gitweb/?p=pvdrivers/win/xeniface.git;a=blob;f=src/xenagent/service.cpp;h=9bc5c20767454eaeae4760308d7655580a08e4cb;hb=5c6adcaa423c465de279158c4cc42500627c20a0
> seems to use StoreWrite("control/shutdown", ""), which sounds correct
> (if it really does what it suggests to do). But that's just cursory look
> at the code, I'm not sure if that's even the correct file.
>
> The system is using official build of 8.2.2 drivers.
>
> Original bug report can be found here:
> https://github.com/QubesOS/qubes-issues/issues/7404#issuecomment-1117231111
> (see subsequent comments for details)
>
> Any idea?
The commit you are missing, I believe, is:

commit 4c1d9b0a57a349d9d3ae8c8af2519618c73c40b4
Author: Paul Durrant <paul.durrant@xxxxxxxxxx>
Date:   Tue Apr 10 17:21:38 2018 +0100

    Fix control/shutdown acknowledgement

    The code in FdoSuspend() currently acknowledges a suspend request by
    removing the control/shutdown node from xenstore. This is not correct.

    The documentation [1] states that a request should be acknowledged by
    writing the empty string. This patch makes the code behave correctly.

    [1] 
xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/misc/xenstore-paths.markdown;hb=HEAD#l413
    Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

This is what git says:

git tag --contains 4c1d9b0a57a349d9d3ae8c8af2519618c73c40b4
9.0.0-rc1

... so it was not back-ported to 8.x.

  Paul